Haobo Jiang

Blocking transmission of vector-borne diseases, biocontrol of agricultural pests, and protection of beneficial insects are expected to rely more on our understandings of arthropod immunity. Our group studies molecular mechanisms of immune responses in Manduca sexta, a lepidopteran pest and a biochemical model. Our research has yielded a theoretical framework of an extracellular network of serine proteases, their homologs and inhibitors for studying similar systems in vectors, pests, and others. We explore intricate host-pathogen interactions in the stages of pattern recognition, signal modulation, and execution mechanisms (e.g. melanization, cytokine induced synthesis of antimicrobial proteins). The biochemical and molecular biological studies have provided knowledge on the defense mechanisms of holometabolous insects and beyond.

Research Interests:

- Extracellular serine protease cascades have evolved in vertebrates and invertebrates to mediate a rapid defense response to wounding and infection. We have been investigating the enzyme system and its regulation by serine protease homologs (SPHs) and inhibitors (serpins) in a biochemical model insect, Manduca sexta. In collaboration with Dr. Kanost's group at Kansas State University, we are studying proteolytic activation of phenoloxidase (PO), Spӓtzle, and stress responsive peptide (SRP) precursors. PO catalyzes the formation of reactive compounds to kill pathogens and encapsulate parasites with a melanin sheath. Spӓtzle binds to Toll receptor to induce synthesis of antimicrobial peptides and other factors. SRPs block growth, cause hemocyte spreading, and stimulate immune signaling.

- Upon binding of bacterial peptidoglycan or fungal β1,3-glucan by their recognition proteins, precursor of hemolymph protease-14 (HP14) autoactivates and active HP14 generates HP21, HP2, HP5, HP6, HP8, PAP1−3, SPH1, SPH2, PO, Spӓtzle, and SRPs. We are studying the pathogen recognition, proHP14 autoactivation, proHP5, proPO and proSRP activation by PAP3 (i.e. proPO activating protease-3), and other proteolytic steps in this SP-SPH system. A high Mr complex of SPH1 and SPH2 acts as a cofactor of the PAPs. To ensure these responses are local, potent, transient, and against non-self, the extracellular SPs are down-regulated by serpins after they accomplish their missions. We have also examined the functions of serpin-1 variants, serpins 3−6, 9, 12, and 13.

- We have annotated immunity-related genes in Drosophila melanogaster, Apis mellifera, Aedes aegypti, and Tribolium castaneum. We developed novel methods for automated gene modeling and expression profiling, which strongly supported the genome project of M. sexta. Following an in-depth annotation of the 337 SP-like genes in Anopheles gambiae, we updated extensively the information on their homologs in A. mellifera, T. castaneum, and D. melanogaster. We then revealed orthologous relationships among SPs or SPHs from the five model species to inspire functional studies in holometabolous insects.

- We adopted new sequencing technologies to explore transcriptome of M. sexta. A genome- independent method was developed and applied to quantify changes in the transcriptomes of arthropods. We explored the microRNAs in M. sexta to examine the posttranscriptional regulation of gene expression. We launched a series of studies to identify differences in the proteomes of cell-free hemolymph samples from M. sexta. These analyses revealed features of the proteomes, including correlation with transcriptome data, formation of immune complexes, constitution of the extracellular immune system, and developmental changes. We are now studying cellular immune responses of M. sexta using single-cell RNAseq techniques. On the other end, we collaborated with structural biologists on and off campus and conducted structural analyses of key insect defense proteins by X-ray crystallography and NMR spectroscopy. Together, these data form a solid platform for biochemical elucidation of the immune system and its regulation and for dissemination of knowledge to other model insects, disease vectors, and agricultural pests.